FanBoxes extension adds a new way of creating and using userboxes, based on special pages. When installed, three new special pages will be added: Special:UserBoxes (to create new userboxes), Special:TopUserBoxes (to view most popular ones) and Special:ViewUserBoxes (to view all userboxes).
It also adds <userboxes> and <fan> parser hooks (TODO: document).
Both of these parser hooks disable parser cache.

FanBoxes requires SocialProfile extension and YUI (YUI is used only for the color picker feature on Special:UserBoxes; the YUI files are loaded from Yahoo!'s servers).